Confirming some long-held suspicions, scientists now report a new twist on emotional manipulation: Experiments suggest that men do indeed deliberately anger each other to get what they want.

For instance, Man A in competition with Man B will make his opponent mad if he thinks it will help him win, according to Uri Gneezy, a behavioral economist at the University of California, San Diego, whose study appeared January 13 in the journal Proceedings of the National Academy of Sciences.

Why study anger?

Gneezy and colleagues are interested in what motivates people to make decisions. Strategic interactions with each other appear to be the main factor, he said.

Traditionally, some psychologists and negotiation experts have suggested avoiding emotions in decision-making discussions, even going as far as to say rational people don't use emotions, according to Gneezy, who worked with colleague Alex Imas.

But Gneezy's research has shown just the opposite: "Emotions are what we are," he said.

For the first experiment, the scientists randomly paired participants—140 undergraduate men—and tested the force of their handgrips.

By giving one of the pair the opportunity to anger his opponent by making him do administrative tasks after a first round of tests, the team discovered that the decision-maker strategically angered his opponent when the decision-maker thought it would impair the other's performance—but not when he thought it would benefit his rival.

In the second experiment, which involved 120 undergraduate men, the researchers pitted two random people against each other in a mentally challenging computer game in which participants realized that angering their opponents would help them win.

That's because making the opponents mad would make them perform less well on their task of shooting a digital target.

Why study only men?

Gneezy said that women are harder to study because their emotions are more variable than men's.

Not every expert agrees. Those who assume men are somehow easier to study are "undercomplicating" their hormones, says Kathryn Clancy, an anthropologist at the University of Illinois at Urbana-Champaign who has studied women's hormones for 12 years.

"Men's hormones vary in response to behavioral context and lifestyle perhaps even more than women's," Clancy said by email.

For instance, the male hormone, testosterone, varies with exercise (as progesterone does in women), dominance rank, partnership and marriage, fatherhood, whether men win or lose at games, and even with whether men are cheering for a winning or a losing team.

Taking all those variables into account "makes working on men at least as complicated as working on women. If not more so!" she said.

Why is this study important?

Every decision we make has an emotion wrapped up in it, study leader Gneezy argued.

"Emotions are not something you should ignore," he said.

"It's not a mistake, it's not irrational—instead, we need to learn how to use them."